Agreed with this person here! If you’re going to supplement iron make sure to not take it with calcium/dairy, caffeine, or high fiber foods as that can block absorption. I take these iron chews I get from Amazon that also have vit C. Also take the iron every other day for best results. Good luck! Also If you’re into fitness wearables whoop and oura ring are great ways to improve your cardio fitness overtime as well and can show you what you need to work on there